1. Field of the Invention
The present invention relates to an apparatus for monitoring the condition of the woof in a weaving machine. More specifically, the present invention relates to such an apparatus in a shuttleless weaving machine adapted to detect the breaking of the woof and to automatically stop the weaving machine.
2. Description of the Prior Art
Recently, weaving machines of the shuttleless type, wherein the woof is fed by means of a carrier, an air stream, or the like, while being yielded from a supply, have been put in practical use to replace the more conventional type automatic weaving machines, wherein the woof is fed by the use of shuttles. A variety of apparatuses have been proposed and used for detecting the breakage of the woof in shuttleless weaving machines to cause automatic stoppage whenever a break is detected. A typical prior art apparatus employs a system for detecting the state of tension of the woof by a mechanical means such as a micro switch, dropper or the like adapted to be in contact with the woof. Another type of apparatus employs a piezoelectric detector, to provide an electrical signal representative of the breaking of the woof, by detecting the mechanical vibration of the woof. Photoelectric and electrostatic detection systems, and the like, have also been proposed and put in practical use. However, none of the above described prior art detection systems utilize generation, termination or variation of a monitoring signal in a given range of the weaving cycle of the weaving machine. Therefore, since the prior art systems continually monitor the woof from the start to the end of the travel of the woof, they are liable to cause an erroneous indication of a malfunction, because the woof tends to loosen when the woof is yielded from its supply package making the tension of the traveling woof non-uniform.
For the purpose of preventing the above described erroneous indication of a malfunction, ideally it would be preferable to select the timing for detecting the woof as immediately after the complete insertion of the woof in the warp. However, at that time the travel of the woof is terminated and no signal for detecting the travel vibration of the woof is obtained. Therefore, the ideal timing is not practical for all monitoring modes.
Another problem encountered in the continued monitoring of the woof occurs, since the traveling speed of the woof varies and at midway through the warp comes to a halt before resuming its travel completely through the warp. Therefore, detecting the vibration of woof results in a discontinuous signal over the weaving cycle. Assuming that electrical sensitivity of the woof vibration detection circuit is enhanced in such a manner for monitoring the woof immediately before the woof is completely inserted, it follows that a pseudo woof monitoring signal may be obtained which is caused by noise, and the like. Therefore, even if the woof has broken, it will not be reliably detected. The prior art apparatus, therefore, has been adapted to utilize a detecting range of 5 through 30 centimeters before the end of the fully inserted woof length within the range where stable detection is possible. Such a stable detecting range is largely dependant on the thickness, the roughness, the twisting, the number of twists, the tension and the like of the woof. In any event, the prior art apparatuses for detecting the breaking of the woof within such a stable detecting range have shortcomings in that woof breakage which occurs subsequent to the 5 through 30 centimeter monitoring range is not detected. In order to eliminate such shortcomings, it is necessary to change the relative position where the monitoring means is mounted for mechanically detecting for breakage in the stable detecting range so as to fully monitor the complete length of woof extending through the warp for each weaving cycle of the weaving machine.